Deep brain stimulation (DBS) electrodes and/or shallow electrodes including subcutaneous or sub-dural electrodes are typically connected to one or more active implantable medical devices (AIMD) which provide various types of therapeutic pacing pulses for treating a variety of disease conditions including, but not limited to, epileptic seizures, Turrets Syndrome, Parkinson's Tremor, and a variety of other neurological or brain disorders. Typically these therapy delivery systems involve one or more DBS and/or shallow electrodes that are implanted into or adjacent to the brain matter (through a skull burr hole) with leadwires tunneled to an implanted hermetically sealed electronics module that applies the appropriate electrical therapy. Electrodes implanted deeply within the brain can be unipolar, bipolar, quadpolar, or multipolar, having many channels. Additional electrodes can be placed either subcutaneously or subdurally to create a multiplicity of electrical vectors through brain tissue.
By way of example, FIG. 1 is a side view of a human skull with two quadpolar DBS electrodes 20 and 20″ placed deeply into the brain matter. There are leads 22, 22′ connected to the deep brain electrodes 20, 20′ and routed underneath the skin through a tunneling procedure along the back of the patient's head and down along the side of the patient's neck. In addition to the deep brain electrodes 20 and 20′, there may also be subcutaneous or subdural electrodes 24 and 24″ as shown. In this way, electrical stimulus may be between any of the electrodes or electrode pairs shown on the DBS electrodes 20 and 20′ or between the DBS electrodes and the subcutaneous/subdural electrodes 24 and 24′, as shown. This gives the physician a number of options in terms of electrical vectors for pacing pulses in the brain and for sensing various brain waves.
Leads 22 and 22′ can each consist of a number (bundle) of coaxial or bi-filar leadwires. In this case, there are a sufficient number of leadwires to supply the two DBS quadpolar electrodes 20 and 20′ (total of eight leadwires) in addition to the quadpolar subcutaneous/subdural electrodes 24 and 24′ (a total of eight more leadwires). Accordingly, in the illustrated embodiment, there are a total of sixteen leadwires that are encompassed within the encapsulated leads 22 and 22′.
FIG. 2 is an X-ray tracing of the front view of the pectoral area of the same patient shown in FIG. 1. Illustrated are two implantable pulse generators 26 and 26′, which are typically housed in titanium cans. Since titanium does not show up that well on an X-ray, one can only see the outline of the titanium can, but can also see the internal circuit boards 28 and 28′ inside the titanium housings very clearly. One can refer to prior art cardiac pacemakers for a better explanation of what these devices look like. One can also see the leads 22 and 22′ whose proximal ends plug into connector blocks which are part of the implanted pulse generators 26 and 26′, typically in accordance with AAMI Standards or ISO Standards, such as ISO IS1 or IS4. These leads can also be permanently connected via a hermetic seal without the need for an intermediary connector block.
FIG. 3 is a line drawing of the front view of the human head of FIG. 1, further showing by way of example the locations of the two prior art DBS electrodes 20 and 20′.
FIG. 4 illustrates the quadpolar electrodes 30 of the deep brain electrode 20, and also the associated multi-wire electrical lead 22 that, as previously mentioned, is routed between the skin 32 and the skull 34. A burr hole 36 is typically formed through the skull 34 to gain access for implantation of the DBS electrode assembly 20.
There are a number of problems associated with the prior art illustrated in FIGS. 1-4. One is the difficulty, due to the length of the leads 22 and 22′, in routing the leads 22 and 22′ from the pectorally implanted pulse generators 26 and 26′ across the pectoral area of the chest, up the side of the neck and the back of the skull, and then finally down to the DBS electrodes 20 and 20′. Associated problems include the tendency for there to be infections, reliability issues due to lead breakage associated with the constant twisting, turning and bending of the head and neck area, as well as the fact that it has been well demonstrated that long leads can be problematic during medical diagnostic procedures, such as magnetic resonance imaging (MRI). U.S. Pat. No. 7,363,090 and U.S. Patent Publication Nos. 2007-0112398 A1, 2008-0071313 A1, 2008-0049376 A1, 2008-0132987 A1, 2008-0116997 A1, and 2008-0161886A1 are all incorporated herein by reference for an understanding of how the electromagnetic fields from MRI couple to implanted leads and can cause associated overheating and thermal injury.
There are also a number of problems associated with the surgical procedure involving tunneling of the leads under the skin and over torturous bends and surfaces. Not only are there issues of infection, the tunneling tools sometimes cause injury or poke through the skin and have other deleterious effects.
Moreover, there are general electromagnetic interference (EMI) problems associated with prior art implanted brain pulse generators or brain stimulators that also do sensing. The long leads 22 and 22′ act as antennas and pick up stray electromagnetic signals from the patient environment. For example, electromagnetic emitters such as cellular telephones, microwave ovens, RFID readers and the like, can all induce signals on these leads which can disrupt the proper operation of the implanted pulse generator and/or its sensing signals.
There are additional problems associated with the relatively long electrical leads 22 and 22′ that run from the implanted pulse generators 26 and 26′ up to the location of the subdural electrodes 24′ and the DBS electrodes 20 and 20′, FIG. 5 is a top view of a sketch from an actual MRI slice taken through a patient's skull. In this case the MRI scanning of the patient was inadvertent. That is, the radiology technician was not aware of the presence of the deep brain stimulator. One can see an area 38 of a severe brain lesion that was caused by thermal injury during this 1.5 Tesla MRI procedure. This is a dramatic illustration of how the pulsed RF field produced by MRI equipment can overheat long implanted leads and how sensitive the brain is to thermal injury. This patient experienced severe neurologic disabilities due to this traumatic injury.
Accordingly, there is a need to eliminate, as much as possible, the associated lead wiring that runs from the implanted pulse generators 26 and 26′ up to the location of the DBS electrodes 20 and 20′. The present invention addresses this need and provides other related advantages.